Interpreting QVtrace Analysis Results

No violations exist: This implies that the model is consistent with the stated constraints for all possible input values, and at all times. As shown in the left image, the Results tab will turn green when no violations exist.

No violations exist up to a maximum time (tmax): This implies that the model has been proven to be consistent with the constraints within the implicit temporal logic of the system. However, there is no guarantee that at some greater time step a violation may occur. In these cases, the results tab turns blue, and absolute time references may be required to assess the validity of results over larger timeframes. This is accomplished by including an explicit time reference {t} to the parameters present in the constraints.

Violations found: This states that inconsistencies between the constraints and the model have been found (the term violation arises because QVtrace works by initially assuming the model and the constraints are consistent with each other, and then proving this is the case or finding that this consistency has been violated). The Results tab turns red in these cases.

When violations have been found, the Results tab will be expandable to show which constraints are violated by the design.

As seen in the example image above, two of the constraints have been violated by the design and this number of violations is shown on the red tab. Pressing the ‘+’ sign on the right-hand side of the tab expands it to show the violated constraints. Each of the violated constraints can in turn be expanded in the same manner to show the evaluated time steps as well as the variable values at each time step.* Each time step can also be expanded to show the variable values used to demonstrate the violation.

Vertical tabs on the left-hand side of each expanded time step in the results tab show either top-level variables (highest level design inputs and outputs) or all of the variables including all inputs and outputs for each component in each subsystem.

To search for specific variables in the violated constraints, click on the magnifying glass icon on the right side of the red tab. This helps focus on a single variable’s values for all evaluated time steps.

* Note that the number of time steps evaluated depends on the implicit temporal logic of the design. The more complex the time dependence in the model (due to delays, integrators, etc…) the more time steps need to be evaluated to complete an entire period of this temporal logic of the design.